1. Field of the Invention
The present invention relates to an electronic type protective relay. In particular, the mechanical structure of the electronic type protective relay collaborates with the electronic device in the electronic type protective relay. Therefore, the mechanical structure takes off the contacting terminal so that the circuit is open during overloading, and then the mechanical structure is reset to recover the circuit from an open-circuit.
2. Description of the Related Art
The relay has been developed for a long period of time and adapted in different industrial products. The electro-magnetic relay is widely used in circuit and is a common control device in the electric machinery. The electronic type protective relay, such as a motor overload relay, is usually used for automatically tripping the circuit in mechanical equipment so as to protect mechanical equipment in case of circuit overload. FIG. 1 is a schematic diagram of an application of an electronic type protective relay according to the prior art. The electronic type protective relay 91 is installed between an electronic-magnetic contacting device 92 and a load 93 (such as a motor). The electronic type protective relay 91 comprises an electronic sensing device to detect an overload, and a set of mechanical structure that collaborates with the electronic sensing device to automatically trip the contacting terminal so as to open the circuit. Furthermore, the electronic type protective relay 91 provides an auto reset function after a default period passes. There is also a manual reset button on the panel for providing a manual reset function. The electronic-magnetic contacting device 92 is used for cutting off or conducting power between the frequency converter and the motor. When power is directly connected to the motor without passing through the frequency converter, the electronic-magnetic contacting device 92 is used for cutting off or conducting the direct power connection between the power source and the motor. Currently, an electronic type protective relay usually comprises a manual stop button and a reset button on the panel to fulfill the requirements of the circuit. The manual stop button is pressed by the operator to stop the operation of the motor. The reset button provides a manual reset function and an auto reset function. The manual stop button and the reset button operate in cooperation with permanent magnets, coils, magnetic core elements and a tripping rod to provide the above functions.
However, the above electronic type protective relay adopts a stop operation and a reset operation that are operated separately and has two buttons. The assembly of the mechanical structure is complex and time-consuming. The number and cost of the components are therefore increased, and the assembly cost is also raised. On the other hand, the two buttons of the prior art electronic type protective relay only provides three functions—manual stop, manual reset and auto reset. The operation rod cannot perform the auto reset and the stop function simultaneously. In addition, the design requirement of magnetic path is much more for accomplishing stop, manual reset and auto reset functions instantly, so that the designing and manufacturing are more complex. After developing for a long period time, there are some conventional products.
For example, the U.S. Pat. No. 5,332,986 is published on Jul. 26, 1994 and disclosed a relay structure. The relay structure includes two buttons that are used for test and reset individually, and a steel follower is a required element for accomplishing the functions. When an actuator bar moves to the tripped position, the steel follower slides against a yoke member and has one end abutting the steel portion of the actuator bar at its first end. Then, the steel follower is magnetically attracted to the actuator bar and forms a close electromagnetic loop. When an overload condition ceases to exist and no current flows through coil, or when the reset button is depressed, the magnetic attraction between follower and the first end of the actuator bar is sufficient so that when the follower is moved downward the first end of the actuator bar moves with it. Thus, an electromagnetic loop of reset condition is formed and the actuator bar abuts the yoke member again at this time. Therefore, no matter in a tripped position or a rest position, the prior art both requires a close electromagnetic loop.
Also, the U.S. Pat. No. 5,994,987 is published on Nov. 30, 1999 and disclosed a relay structure. The relay structure includes a housing and a spring latching finger. The spring latching finger has a fixed end. By abutting the fixed end against the housing, the spring latching finger is fixed to the housing. The spring latching finger has an upturned end that is adapted to embrace and latch against latch surfaces to lock a latch lever for a manual operation function. Although this prior art does not need a complex electromagnetic loop, however when operating with a manual operator, the spring latching finger either latches against the latch surfaces for a manual condition or is received in a detent surface for an auto condition. Unless turning an additional stop button, other function cannot be achieved. Furthermore, this prior art needs numerous elements so that the mechanism design is more complex.
The prior art electronic type protective relays are difficult in fabrication and inconvenient in application, as mentioned previously. They cannot perform the auto reset and the stop function simultaneously, and the manual reset and the stop function simultaneously by utilizing a simple magnetic loop. It is therefore very important to provide a new electronic type protective relay to overcome the above-mentioned drawbacks.